What happens if a black hole comes too close to Earth? Physicists explain

Scientists have long studied the existence of black holes, but we still don’t know much about them. The first strong evidence of a black hole was found in 1964, and they are considered some of the most mysterious objects in our known universe. Once something crosses a black hole’s event horizon, nothing can escape, not even light itself.

So, what happens if we get too close to one, and could we survive it? Here’s what physicists explain.

When an object gets too close to a black hole, the part nearer to it feels a stronger pull than the part farther away. This difference is called a tidal force. And near a black hole, the object would be stretched into a long, thin shape, a process often known as spaghettification. 

Physicist Stephen Hawking described it in his book "A Brief History of Time," where a fictional astronaut is "stretched like spaghetti." Around supermassive black holes, stars can be flattened instead, in what's called "pancake detonation."

In addition to the effect on the object, there would also be an effect on time. According to NASA, the strong gravity curves of a black hole stretch the fabric of space-time. This means near a black hole, time passes more slowly closer to a black hole than farther away. This is called time dilation.

As the object gets close to the event horizon, which is the point beyond nothing can escape, it would then move slower and slower until it looks completely frozen.

Charles Liu, an astrophysicist at the American Museum of Natural History's Hayden Planetarium, explained, "Furthermore, as you fall, there are things that have been falling in front of you that have experienced an even greater 'time dilation' than you have. So if you're able to look forward toward the black hole, you see every object that has fallen into it in the past. And then if you look backwards, you'll be able to see everything that will ever fall into the black hole behind you.

"So the upshot is, you'll get to see the entire history of that spot in the universe simultaneously," he added, "from the Big Bang all the way into the distant future."

If there’s a black hole with the same mass as our planet, it would appear smaller than a marble. But even then, the gravity of it would match Earth’s. If this black hole raced toward us at nearly the speed of light and passed close without hitting Earth, the planet would suffer severe damage. 

The side nearest the black hole would feel a far stronger pull. This would result in massive earthquakes, giant tsunamis, and even eruptions from long-dormant volcanoes.

When a massive star reaches the end of its life, it can collapse and form a stellar-mass black hole. A black hole with 10 times the Sun’s mass entering the outer solar system would first make its presence known in the Kuiper Belt.

Earth wouldn’t have much time before the situation became far more serious. The Moon’s orbit could shift and cause extreme tidal changes, while even a small change in Earth’s tilt could disrupt weather patterns worldwide.